Power supply system



April 29, 1941. F. sHoUP ErAL POWER SUPPLY SYSTEM Filed sein. 1e, 193s v Patented Apr. 29,

UNITED STATES PATENT OFFICE v I I I r V v rowm rsrsmrr y v l Y Frederic Shoup,'0aklyn, N. J., and Alexander D.

Burt, Narberth, Pa., assig'nors to Radio Corporation of America, New York, N. Y., a corporation of Delaware Application september 16, 193s, serial' No. 689,720'

claims (ci. 1v1-9i) 'The present invention relates to power supply systems for radio receiving apparatus and the like, and has for itsv primary object to provide an improved supply system of that character which is adapted to operate in connection with a low voltage battery as the sole source of operating current for lthe apparatus.

Battery operated power supply systems are at present of increasing commercial importance in connection with automobile radio receiversv andv the like, and in accordance with the invention,

are provided with means whereby the usual 6-8 volt or other storage battery source of ignition, starting and lighting current. may be utilized successfully as the source of operating current for all circuits of the entire radio receiving or similar apparatus.

employed in providing battery operated radio apparatus of the automobile receiver type with suitable operating current from low voltage battery sources. In a major portion of' installations in automotive vehicles, boats, and isolated locations, however, the problem of power supply hasbeen solved to a limited extent by the use of low voltage batteries, such as an ordinary storage battery,

for lament or heater excitation, with fB batteries and C batteries for'supplyingthe necessary anode and grid potentials. However, the short life, added weight and other disadvantages inherent in the use of such ,batteriesin general are not compensated by the simplicity of the incase, however, a motor-generator device is involved, with additional initial expense for that item of the system.

It is, therefore, a further object of the present invention to provide an` improved power supply system for radio and like apparatus which may be operated directly from a low voltage or automobile storage battery as the sole source of power for all circuits of the apparatus, without the use of "B" batteries and without the use of motorgenerator equipment for transforming the battery current.

In carrying the invention into eifect, a simple vibrator-rectier system is employed, and is so arranged that high frequency disturbances, heretofore considered as unavoidableas the result of operation of vibrators, are prevented from interfering with the. operation of the radio-apparatus.

This is for the reason that in an automobile, for example, the vibrator-rectifier system receives current from the automobile battery and is thereby connected with the wiring which extends throughout the automobile chassis. It is also connected with al1 of the circuits of the radio apv cillations within a wide frequency range extend- A Heretofore, various supply systems have been ving throughout both, the audio and radio frequency ranges-even into the ultra high frequency range, so that radio interference from Vibrator type rectiers has been considered as both dimcult and costly to eliminate.

It is, therefore, a further object of the present inventionv to provide an improved power supply system for radio receiving apparatus and the like of the vibrator-rectiiier type wherein the radio interference therefrom, ordinarily experienced, is substantially eliminated. t In carrying into effect the above and otlie objects of the invention, the vibrator-rectifier system is electrically isolated from the chassis wiring of the automobile. including the power source or battery, as is also the filament heating and the plate supply systems for' the radio apparatus from both the vibrator-rectifier system and the chassiswiring. This is accomplished by properly separating the supply system into suitable units and by providing separate ltering at certain points in the supply system in connection,

vdirect-current source, at a suitable potential,

adapted to provide a relatively heavy operating current over such periods of time as such apparatus is ordinarily.operated.V The invention will however, be better understood from'the f following description when vtaken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

In the drawing, Fig. 1 is a schematic circuit diagram of a radio receiver provided with a power supply system embodying the invention, and Fig. 2 is a curve diagram illustrating the operation of thepower supply system of Fig. 1.

Referring to Fig. 1, the dotted outline indicated at 5 represents a shielded radio receiver unit, to which is connected a power supply unit 6, in turn connected with a single source of operating current or power l.` Ihe receiver indicated may be considered as an automobile radio receiver, with the power supply means 1 provided by the automobile storage battery. The battery also supplies-the usual ignition, starting and lighting systems represented by the rectangles 8, 9 and I0, respectively, and the operating switches Il, by which said systems are con` nected with the battery throughthe supply or chassis wiring of the vehicle, indicated generally at I2.

In'the present' example, the receiver 5 is fully enclosed and shielded, as indicated by the dotted outline, as a single unit with the supply unit 6 andaI loud speaker device I5. The supply unit may also be enclosed by extending the shielding as indicated at 6a. A suitable ground connection indicated at I6 and two connection leads only are required for the receiver. The two leads include a shielded antenna or signal input lead I1, and the battery or power supply lead I3. 'I'he ground connection is made in any suitable manner, as by mounting the apparatus in the vehicle on the frame, thereby simplifying the installation of such apparatus. It will, therefore, be seen that such installation involves merely securing the receiver in place in the desired location and making two lead connections.

The ground connections to the chassis, however, represent any suitable connnon return circuit for the4 various circuits of the apparatus and the power supply source or battery 1. It should be understood that such connections may be made to any other common conducting return means other than the metallic chassis of the vehicle o1' of the receiving apparatus. All wiring connections are preferably grounded and, accordingly, the grounded chassis return system as a preferred embodiment is shown in the drawing.

By way of example, the receiver 5 is provided with the usual electric discharge devices or tubes and circuits therefor, including a radio frequency amplifier device or tube I8, a second device or tube I9 in cascade connection therewith, which second tube may be a combined detector and oscillator, and an output device or tube 20 connected with the loud speaker device I5. Intermediate apparatus and tube circuits which do not primarily concern the invention are indicated by the block diagram 2|. 'I'he tubes are provided with suitable filament or heater supply leads 22 having grounded return connections as indicated, and are connected with a filament or heater supply lead 23 from the supply unit C. The tubes are also provided with suitable anode potential supply leads indicated at 24, and screen grid poten- With further reference to the supply circuits, it will be noted that the tubes are arranged to be provided with grid bias potentials from self-bias resistors 29 in the cathode return leads 30 of the tubes indicated. 'I'his is a preferred arrangement for bias potential supply, since the circuits are simplified, and shortened in the apparatus, and the anode potential available is sufllciently high, whereby the bias potentials may be obtained in this manner.

The low voltage storage battery current is supplied to the receiver through the receiver power supply lead I3 which extends through a groundtial supply leads indicated at 25,`connected with an anode or positive B supply lead 26 from the supply unit 6.

The loud speaker device I5 may be of the elec.

trodynamic type and may also be provided with a suitable held winding' indicated at 21. This is also connected with the filament or heater suptive. lead of the battery.

ed shield, indicated at 3|, and a power switch 32 for the apparatus, which switch may be remotely located. 'Connected with the lead I3 from power switch 32 is the filament or heater supply lead 23, and a vibrator supply lead 33, forming branch circuits from the power switch and the lead I3. A suitable pilot light is also con nected from the power switch to ground at the remote location as indicated at 34.

Interposed in the lament or heater supply lead 23 is a high frequency filter choke coil 35 comprising, in one embodiment of the invention, a few turns of wire and a suitable by-pass capacitor connected to the output or filament end of the choke coil between the lead 23 and ground, as indicated at 36. The functions of this coil and condenser lter will hereinafter be described. Generally, it is an ultra high frequency lter for ignition and vibrator electric disturbances located at a point in the system where it has maximum elect for eliminating such disturbances. The filter choke coil 35 is therefore, preferably of few turns and of no appreciable resistance. In any case however, it is of such impedance that it may provide with the condenser, an effective filter for the disturbances at any particular frequency.

The filament or heater circuit' formed by the lead 23 and the grounded returns therefor, is operated directly from the battery source without interposing any current limiting resistors. The vacuum tube devices in the apparatus and the loud speaker field are, therefore, preferably arranged to operate at the voltage supplied by the battery 1, which is usually substantially 6-8 volts.

The anode or plate supply lead 26 is provided with operating potential from the same battery source, and is energized through the vibrator lead 33 and the high vvoltage supply means which includes a vibrator-rectifier unit indicated at 31, a step-up transformer indicated at 38, and electrical circuit filter means indicated as two units, 33 and 40, and as a separate radio or high fre- `quency choke coil 4 I.

l The construction of the vibrator unit per se is shown, described and claimed in a copending application of Emil C. Guedon, Alexander D. Burt, and Frederic Shoup, Serial No. 713,324, filed February 8, 1934, assigned to the same assignee as this application, and now Patent No. 2,063,311.

The vibrator-rectifier unit comprises an armature 42 which isfcaused to vibrate under the action of a suitable operating electromagnet 43 controlled by Aoperating contacts 44 connected in circuit between the electromagnet 43 and a ground lead indicated at 45, whereby it is connected with the grounded, and in this case, nega- Ihe other or positive supply lead for the electromagnet is indicated at 4i. It will be noted that this is not grounded ply lead 23 through a'supply lead indicated at 2l. 75 and is connected as a branch lead with the lead l to the battery.

3i through the lter 33,' which hereinafter be described. Operating current from the battery is supplied through the electromagnet 43 and the contacts 44 to the ground and is returned -Two sets of xed vibratory contacts 41 and 48 tacts 41a and 48a carried by the armature.. to a1- ternately connect the terminals. of the secondary 49 and the primary Il with ground Vthrough are arranged to operate in connection with conthe armature '42. For vthis purpose, the con- .tacts '41 and 4I are connected respectively with provides tno nigh potential output terminal or the vibratorrectiiierl unit and is connected with the high voltage positive "B supply lead 26 through ajsuitable audio and lhigh frequency lter indicated at and a second lter' choke coil 4I. The filter 40 comprises the usual audio frequency choke coil indicated at 54 and suitable filter bypass condensers li connected with the ture vibrating ata predeterminedfrequencyin response toopening and closing of the vcon,- tacts 44. The operating current for the vibrator flows through the supply lead I3. the filter 39,

the lead 46, to the magnet-43, and back tothe battery through the contacts 4f armature 42,

4and the ground lead 45.

TheA opening and closing of the 'contacts 4141a swerve alternately to energize each half of the primary winding I0. The current flows in common with the vibra-tor current through the .branch lead 5I and vcenter tap 5I, thence alternately through each half `of the primary winding, the contacts .41 and 41a, and returns to the battery through the amature 42 and the ground lead 45.

It will be seen that by operation of the contacts 41-41'a, each half of the primary winding is alternately energized through the center tap 5I. At the same time, thel current induced in the secondary winding 49 iiows alternatelyfrcm y each half of the winding toward the center tap I2 to which the positive lead 26 connects, as each half of said winding is alternately connected to ground through the contacts .48+48a. While a reversal of the flow of current in the primary ground. This nlter is preferably enclosed in a suitable grounded shielded container indicated by the dotted outline. 'It will be noted that the adio frequency. filter is connected between the adjacent to the terminal l52 in the high potential output circuit.

It will further be noted that the audio f requency filter is of the capacity type having one of the filter condensers i5 connected acrossI the high voltage output circuit preceding the choke coil Bt.

I'he shunt filter condenseris therefore connected directly across the load circuit without any appreciable impedance between it andthe transformer. It has been found that this con- A anode or plate supply lead 2l and the high' potential output center tap terminal 52 directly nection iseiective in further reducing the tendency for sparking at the contacts as distinguished from a lter having an inductance as the first .f element thereof. A condenser type lter is at present preferred.

The audio frequency filter is followed by a high frequency lter means indicated by the highfrequency choke coil 4|.

high capacity, and a high frequency bypass condenser to ground, indicated at 5B, more adjacent to the vibrator rectier. v

The operation of the system is as follows:

rent to` flow through the supply lead 2l and the various tubes, as well as to the loud speaker field, with a return path to the battery /through the ground. Simultaneously with the excitation 'of the filament or. heaters and th'e eld of the loud speaker, the vibrator I1 is put into operation by energlzation of the buzzer magnet, the arma- 75 between the contacts,

The radio receiver is energized by closure of the switch 32 which permitslament heating curwinding` is thus effected, the operation is such that the current impulses in the secondary windling are in the same positive direction toward the terminal 52 of the secondary winding. A

,pulsating direct current is therebydelivered to the terminal 52 and issuitably smoothed for use inthe plate and other circuits of the receiver by the filter 40. For suppressing the spark at the contacts and for iiltering purposes, condensers are connected n. across each of the pairs olf-contacts 41 and 41a" as indicated at B9, and a resistor Il is connected across the contacts 44. The resistor 60 is effectively in shunt to the contacts l44 to absorb the operating Spark or energy caused by the opening or closing of the contacts 44, while the condensers ,I8 are eii'ectively arranged to tune the primary winding il whereby the contacts 48-48a are opening and closing at substantially the zero difference of potential point of each half cycle, thereby substantially eliminating sparking at the secondary contacts.l The primary contacts 417-414 likewise open and close during the zero potential difference point because of the coupling between the transformer windings. Therefore, with condensers of a value to tune the secondary, no sparking occurs at either setof contacts.

It has been found that the length of the airgap determines to an appreciable degree thecondenser size and that the secondary winding may be tuned to a frequency so related to the fre--l quency at which the connections at the contacts Aare made, and forthe duration of' said connections with the winding terminals, that the connections are made at substantially zero difference of potential between the contacts when they are l lust opening and Just closing, that is, when openfrequency of vibration and the time spentin` con- Y tact so'that the .voltage between the contacts shall not produce ionization of theair in the space shown diagrammatically in the drawing, with a ground connection, as indicated, to the ground lead 45 for the unit.

'It has been found that the condensers may be connected with the terminals of the primary winding of the transformer in a similar manner, but that relatively high capacity values are required if the condensers are connected with said primary winding. Therefore, the connection, asJ

shown, is at present preferred. I i

It will further be noted that in accordance with the diagrammatic showing in the drawing, opposite halves of the secondary and primary windings 49 and 50 are approximately simultaneously connected to ground through the closure of the contacts 41, 41a, 48 and '48a of' the vibrator-rectiiier unit. This is for the purpose o f providing positive polarity for the output current from the terminal 52.

The hoke coil 3i and by-pass condenser 3G. locatedas shown, provide a high frequency lter for removing from the filament heating circuit `any of the ultra high frequency waves generated by the vibrator and which would tend to be transmitted to the radio apparatus connected with the filament heating circuit. By Way of example, it has been found that a small solenoid `winding of 3 to 20 spaced turns of a diameter somewhat less than 1' together with a filter confdenser of 60 -2400 micro-nuorofarads capacity has eliminated ultra high frequency in- -terferencefrom a receiving system as shown.

Likewise, `in the opposite branch lead 33 for the vibrator system is also interposed a choke coil and condenser filter combination 56, Il and 58, re-

spectively. In the present example, a condenser 13 may be substantially the same value as the `condenser," and the coil may have approximately v50 turns on a small diameter form, such as a fraction of one inch.. This filter serves to 4. prevent vibrator signals within the broadcast and high frequency ranges from reaching the autofmobile chassis wiring through the power `contween the vibrator-rectier and the filament cirnection and is. at the same time, interposed becuit thereof'to further prevent interference in the If the polarity of the primary source is reversed from that shown in the drawing. as in an automobile installation wherein the positive and *not the negative lead is grounded, the secondary terminal leads are reversed to maintain the center tapas the positive output terminal.: However, the primaryy terminal leads instead may be reversed for the same purpose, if desired.

The current set up in the primary of the transformer serves to produce a higher voltage in the .secondary 49 since the transformer is Aprovided with a step-up ratio from the primary tosecond-4 ary. 'Ihe step-up ratio is sufilcient to provide a desired potential at the high potential output terminal or lead 26. For example, in a present embodiment of the invention, the voltage provided is substantially 270 volts, direct current,

from a 6 volt direct current applied at the supply lead I3.

'I'he transformer'should be of auch design that the exciting current is low at all times relative ing the filament heating circuit.

In addition to the condenser 58 there is also A provided a -lter condenser i1 for absorbing other high frequency pulses resulting from operation of the vibrator, and as a smoothing means for the system. This condenser may have a relatively high value such as .microfarad i For ultra highf frequency signals generated by vthe vibrator, the condenser Il also cooperates with .the choke coil 35 as a nlter means for preventing such signals from reaching the filament ,heating circuit 23. It should also be noted that whereby the circuit is further protected from to the load current. Furthermore, in maintaining a low exciting current, the transformer should preferably operate at a pointy wellbelow the knee of the'saturation point atthenormal battery supply voltage. This is particularly imknee, the exciting current impulses may reach excessively high values and necessitate av relatively heavy condenser load on the secondary or the primary winding to absorb the. energy which would otherwise cause excessive marking at the such interference.

It-has also been found that more quiet operation is obtainable by placing the filter choke coil Il adjacent to the receiver, with the audio frequency filter ll adjacent to the transformer 33 and the high voltage tap 52. In this way the audio frequency filter Il is followed in the po?. tential output circuit by the higher frequency nlter provided'xby the choke coil Il. It has'been found that this filter may be provided by a choke coil of 250 universally wound.

It will be that the filter Il, the rectifier unit 31, andthe ktransformer 3lY are all provided with shielding: which is srounded. In an automotive vehiciathe ground is, of course. made to the chassis4 or frame thereof. The shielding for the transformer may take the form of a o5 unit lshield indicated `at 33a or a shield'between contacts, that is, to counteractfthe lowering of the inductance caused by the saturation.

Accordingly, in connection with auch battery supply systems, it has been found that the transf former should be provided with a primary having a relatively high inductance whereby it may operate with relatively low exciting current under all conditionshwhich may be experienced with increases in the supply voltage. 4

it and the radi receiver such as that indicated at Io and hereinbefore referred to.

Tracing the supplycircuit from the source or battery. 1.*it will-be seen that the power switch :I2 is connected in circuit through a shielded extension lead, and that the lead then enters a completely shielded apparatus, including in turn separate and shielded units all grounded to the chassis. Furthermore, it will bc seen that a supply lead is then branched and leads out to a filament heating circuit and loud 4speaker. eld

- in one branchthrough an ultra high frequency filter, and through the operating unit to another branch and a high frequency filter to which is added a smoothing lter. The filament heating, held, and vibrator circuits all return to thebattery through the ground, each half of the 'pri'- mary winding being alternately connected-incircuit by the operation of the contacts I8 and 48a. Two high frequency filters are therefore interposed between the vibrator. and th'e filament ated well below the knee of the saturation curve.

For that reason the secondary condensers may further bereduced in size, and hence in cost.

vthe transformer may be properly loaded` for' heating circuit and one between the vibrator and the source 1 and the connected wiring about the automobile chassis.'

It will, therefore, be noted that there is also interposed between the vibrator and the supply circuit for the radio apparatus, a pair of series connected filters similar to that interposed in the nlamentcircuit.

Through the medium of the transformen. the plate supply circuit 'is separatedl from the power supply circuit and the chassis wiring of the automobile, and through operation of the contacts 41 and 41a each half of the secondary is alternately'connected to ground; therebyproviding a separate output circuit 4from the input circuit of the power supply system.

From the foregoing description it will be seen f that the vibrator-rectifier system supplies both anode and grid potentials to the circuits of the radio apparatus, and that in order that the apparatusmay function properly, the potential supply must be steady. This is lparticularly true if a In addition to the Vproper filtering of the cir.- cuits of the supply systemat points and in a manner which has been found to be most effective as hereinbefore described, it willjbe noted that a'full wave rectifier action is obtained'py providing both the primary and the secondary 'of the power transformer with a tap between"y its terminal ends. In the present embodiment,'?'the tap is provided at the center of each winding. and by connecting the terminals of each winding to the contacts of the vibrator, the vibrator arm and the-center taps of the windings are utilized as sources'of input and output voltages.

'Ihe vibrator arm is preferably common to both the primary and secondary circuits and represents any suitable means for alternately connecting rst one half and then-the other half of each' in circuit. -Thus in operation,

the input low voltage current from the battery rst across one half and then'across the other half of the primary of the transformer. This results in a pulsating direct current applied to the primary in an alternating direction. and causes'the flux in the transformer core to vary from a positive to a negative value periodically. The alternating current. voltage 4set up in the secondary ofthe transformer is rectified by the loud speaker is employed, as in the usual automobile radio receiver, for example.

Thesecondary vibrator contacts function in a similar manner to those on the primary side and serve to reverse the alternations applied to the secondary of the transformer and the load,

`whereby a pulsating high voltage direct current is obtained from the secondary center tap.

By tuning one of the transformer windings,

phased to permit the contacts to open and close at substantially zero potential diiference, whereby sparking is effectively eliminated. The rectifying contact changes are then made in approximate synchronism with the pointsof zero potential diiference between the contact means. As has been hereinbefore pointed out, the secondary is the preferred winding for. the reason that the condensers employed for tuning `or loading may .be of relatively low capacity.

Ineffect` the output or load circuit isprovided `with a condenser load which is applied alter- .natelyto each half of the secondary to load it s* the frequency. of operation, which is approxi..

4 mately 70'cycles in the present preferred embodiment of theinvention.

The output or load circuit is further provided with a condenser load forming the .input eleinfent of the'low or audio frequency filter. As hereinbeibre been pointed out, the .condenser "tf o`f filter is preferred for the reason that an i' tial condenser in shunt to the output or load cinicuit is presented to the output current from vthe transformer.- In any powerysupply circuit, in case a filter of the type shown 'is unnecessary,

4then in any case it is preferable that the load circuit is shunted by a relatively large filter conthe primary vibrator contacts function to connect operation of the secondary contacts which operate in synchronism with the primary contacts.

The transformer has a step up ratio whereby the secondary voltageis considerably greater than that of the primary, as before pointed out.y

The transformer may also be utilized as a ma terial aid in reducing sparking without the use of excessively large absorbing condensers 'for the reason that, as also hereinbefore pointed out. the primary of the transformer `may have a relatively high inductance'so that it may be oper-- has been herein- I.

'denser adjacent to 'the output terminalsl of the power supply meansA in the load circuit, without the interposition of any circuit element having an appreciable impedance to current ow.

The condenser load for the output or load circuit is connected between the load circuit lead from the secondary center tap. and the return lead or ground. The other loading condensers for the .output circuit or secondary for loading or timing the secondary winding to effectively' 'neutralize for the exciting current of the transformer. are connected between the terminals of the secondary each tothe load circuit return lead or ground, whereby said condensers are,'in y "effect, connected in series with a center tap con- 1 I:section to ground. The oondensers may, thereforebe of relatively low capacity and since they -are in series, they may be of a lower voltage ratlng and cost. y

. has also been found that this series center tap connection for the loading condensers materially aids inthe prevention of radio or high freouency interference through 4the output or* tacts Il and indicates the voltage wave shape .resulting from operation of the system. It may sponding primary and secondary contacts Il and 48. The contacts remain open while the armature is traveling across the gap over the curve from the point A to the point B where the contacts l'la and 48a close in the opposite direction. The voltage wave immediately reaches the point C in a. maximum positive direction and the voltage wave remains at that value until the contacts again open at the point D.

The points then remain open over the curve from the point D to the point E when they close again in the same direction as they were up to the point A, and the voltage immediately reaches a maximum negative value F, which it retains terminal ends thereof, a high voltage output lead connected with the secondary tap, an audio frequency lter means in said lead adjacent to said tap, a. low voltage supply lead connected with the primary tap, a cathode circuit forming a branch connection with said lead, high frequency lter means interposed in each of said branch connections whereby said iilter means are connected in series between said primary center tap and said cathode circuit, means providing returns for said low voltage supply and high voltage output leads, and vibratory contact means having reversing contacts connected with the terminals of said transformer windings for simultaneously connecting one of the terminals of each of said windings with the circuit return means therefor.

2. A power supply system for radio receiving apparatus and the like including in combination, a transformer having primary and secondary windings each provided with a tap between the terminal ends thereof, ahigh voltage output lead until the point G is reached. when .the contacts again open and remain open over that period represented by the curve between the points G and H. i

The portions of the curve betweenpoints A and B, D and E, and Gand H, for example. represent portions of a damped voltage wave or oscillation in each instance, the length of which is determined by the inductance of the transformer winding and the capacity of the shunt condenser arrangement. These oscillations are cut oi by the closing of the contacts at the points B, E, and H in the curve diagram shown.

As the vibrator rectifier unit continues in use over an extended period of time, the contacts 4wear gradually and cause the air gap between them to widen. This has been found to change the period of time over which the contacts are open but not to change appreciably the periodv oi' time during which the contacts are closed. This causes the curve B gradually to assume the shape shown by the dotted curve Il. During this change the point E, for example, gradually moves down the slope of the curve lDE until it crosses the zero airis and finally reaches a point such as K, at which time, it has been found that the device may become defective in operation because of instability. During this time, the point E, for

this operating condition over an extended riod, the condensers Il are initially provided with e. slightly excessive value se that the point E and the corresponding points. B and H, for example, are slightly-spaced from the lzero axis.

It will be noted'that, as the curve tl gradually widens to assume the form of the curve, the same nat top characteristic is maintained with substantially straight sides. The form-of the curve is therefore at all times substantially a square" wave. i

It will also be noted that the corners of the curve at C and D, for example, are slightly rounded because of the contact and secondary resistance in the circuit. l

We claim as our invention:

l. A power supply system for radio receiving apparatus and the like including in combination, a transformer having primary and secondary windings each provided with a tap betweenlthe connected with the secondary tap, an audio frequency filter means in said lead adjacent to said tap, a low voltage supply lead connected with the primary tap,4 a cathode circuit forming a branch connection with said lead, a high frequency filter means interposed in each of said branch connections whereby said filter means are connected iny series between said primary center tap and said cathode circuit, means providing circuit returns for said low voltage supply and high voltage output leads, vibrator means having a common vibratory arm contact and reversing contacts connected with the terminals of said transformer windings for simultaneously connecting one of the terminals of each of said windings with the circuit return means therefor,

'electrical shield means for said vibrator means,

and a pair of condensers included within the shielding of said vibrator means providing separate alternating current paths 'between a pair of -secondary contacts and the common vibratory arm contact therefor and said shield means.

3. A power supply system for radio receiving apparatus and the like including in combination, a transformer having primary and secondary windings provided with power input and output taps, respectively, between the terminal ends thereof, an output filter means connected with the secondary tap, a low voltage battery supply lead connected with said primary tap, a cathode supply circuit forming a branch connection therewith, a high frequency filter means interposed in each of said branch connections whereby said filter means are connected in series between said primary center tap and said cathode circuit, vibrator means having contacts connected with the terminals ofv said transformer windings for connecting the terminals of each of said windings alternately to ground, the filter means in the cathode supply circuit comprising a high frequency choke coil of relatively few turns, and

' said filter means in the branch lead for said primary tap comprising a choke coil followed in the direction of current flowV by s. bypass condenser Gad* each of said branch circuits including high frequency lter means, a high voltage output circuit connected with said secondary tap. low fref quency lter meansinterposed in circuit between said output circuit andl the secondary tap, a vibrator device having ari-operating winding connected through one of said filters with the supply lead, said device having contacts connected with the terminals of said transformer windings and having an armature providing contacts mov-v l -for one of said transformer windings and having a connection between the junction of .said conv densers and the amature to provide a tuning and high frequency filter means on said trans' former.

5. in an automotive vehicle having distributed supply wiring and a low v'voltage battery source r 2,240,123- 7 mary tap and with the cathode supply circuit,`

of power connected therewith, of means for supi plying operating current to radio receiving apparatus from said source without accompanying electrical disturbances from operation of the vehicle, said means comprising an electrical shield for radio apparatus, a step-up transformer within said shield, a vibratory contact device within said shield, for alternately connecting the termi-- nals of' said transformer windings with said shield, means for supplying ltered electrical current from said source toa tap on one of'said windings, and means for supplying iiltered electrical current froma tap on another oi said windings/.to said apparatus, a lament supply circuit .connected with said source, an ultra high frequency lter in said circuit,- a pair of electric tuning condensersconnected in series across one of said transformer windings, and means providing a connection between the junction of said condensers and said shield.

' FREDERIC SHOUR ALEXANDER D. BURT. 

